I am sure you are weary, worn out, and likely tired of dealing with all the ins and the outs. At some point you loved your wife. You loved her enough during the dating stage to propose to her. You loved her enough during the engagement stage to actually marry her. If she has had issues through all those phases, then you must have loved her enough to not let that deter you. You are weathering a storm right now, and you need all the support you can get, too. Are you seeking outside support in the form of counselling yourself? Either that or a support group? Do you have a friend or relative you can confide in? I do not mean your girlfriend either. The thing you do not want is your marital drama to start overshadowing and clouding the happiness in your relationship, too. Then, you really will feel resentment.
Your wife needs help and support, but you cannot force her to get it. Is she on medicines to help with her depression? You can try to offer support in other ways. You might have to do things like court her again and make her feel special to let her know that you are there and actually interested in what is going on with her. You mentioned that she has separation anxiety regarding your children getting older and not being so dependent on her. That separation is a killer. I know because I am experiencing the first bout of it, and the time has not even come, yet. In her mind, it is probably not just being left out of the relationship, it is not knowing what her role is or her purpose is anymore. That means confidence and self-esteem could be lacking. Does she work outside of the home? Does she have hobbies to keep her busy, or are your children her entire world? Before she was the mother to children who needed her much more and a husband who only loved her. Now, she has children who need her less and a husband who loves another woman and has another relationship. Sprinkle years worth of depression, a shaky marriage, a husband who is clearly tired, and it is the makings of a train wreck.
During this eight month period, were you consistently talking and communicating about what adding a new person to your lives would mean for each of you? What was the consent actually for if it was not for developing a relationship? Is there anyway you can her what she was consenting, too? Was she banking on you not falling in love and just having sex with someone else? Her failed attempts could be indicative of the fact that she was not really into looking for love. If she flipped over you telling her that you were in love with her, that tells me that she never fathomed it would go beyond anything the physical. Sex is different. I can go have random, drunken sex with somebody who means nothing and walk away, but when I open my heart to someone else, that is different. That person will be part of my life, part of my husband's life, part of my children's lives, and a part of my world. The approach and the conversations to that would be different.
Has she ever said what she is jealous of? What is it that you need from your wife? How are you approaching her with these needs? Are you keeping your other relationship out of it when you mention what you need from her? Focus on you and her. "I need to feel loved, and when you shut me out, I feel distant and like you are not interested in what I have to say." "I need to know that you are committed to saving our marriage and that you actually care because I cannot care enough for the both of us." "I need to know what you need from me, and I am not mind reader, so I have no starting point. Would you be willing to help me and let me be there for you like you have done for me in that past?" Keep everything else out of it. Has she ever said what she needs from you to be comfortable and at least content? (Outside of ending the relationship and being mono.) I know that is hard with depression, but even people with depression have high days and low days.
I cannot put a time limit on it for you. If her doctors are not helping, then perhaps she needs a new one who is equipped to deal with the issues and to help her. Have you attended any of the counselling appointments with her to hear what she says? Has the therapist asked that you join her?